The instant invention relates to hydroxyalkylated cellulose (i.e. HEC) derivatives containing pendant (meth)acryloyl units bound to the cellulose backbone, through urethane groups, which are further reacted with a conventional vinylic monomer, and which can be crosslinked to form soft hydrogel contact lenses possessing high oxygen permeability, wettability and mechanical strength.
Hydroxyethyl cellulose has not been proposed as a contact lens material. Vision correction lenses such as contact lenses and intraocular lenses have been known as commercial products for over 25 years. An acceptable lens must be optically clear, mechanically stable, and must provide sufficient optical correction, gas permeability and wettability to insure that the lens is comfortable and safe during use. Gas permeability is important since the corneal surface of the eye respires by obtaining oxygen and other substances from tear fluid and by releasing carbon dioxide and other products of respiration into tear fluid. The intimate contact and position of the contact lens can substantially prevent the exchange of such Constituents between the corneal epithelial cells and tear fluid. As a result the cornea can become starved for oxygen and can accumulate harmful amounts of metabolites within the constituent cells. This can result in corneal edema (swelling) and often extreme discomfort to the wearer. Wettability of the lens is important because a nonwettable lens can be abrasive and irritating to the eye and lid and can cause significant wearer discomfort. A lens must have sufficient mechanical integrity to allow for easy cleaning and handling and maintaining the desired curvature and correction for the individual user. The lens should be immunologically compatible with the eye reducing chances of allergic reaction or toxic response. Further the lens should be permanently dyeable easily manufactured and available at low cost.
In the past contact lenses have been made from synthetic polymeric materials such as plastic matrices based on polyacrylates, polymethacrylates, poly(hydroxyethyl methacrylate), cellulose acetate butyrate, silicones, etc. More recently contact lenses have been made from collagen, a naturally occurring protein. Miyata, U.S. Pat. No. 4,223,984 is primarily directed to a contact lens made from solubilized defatted transparent crosslinked collagen. Miyata U.S. Pat. No. 4,260,228 is particularly directed to an improved collagen gel soft contact lens prepared from an aldehyde crosslinked gel containing a polyhydroxy compound such as glucose. Miyata, U.S. Pat. No, 4,264,155 is primarily directed to an improved lens made from collagen gel to which a water soluble organic polyhydroxy polymer has been added.
Ivani, U.S. Pat. No. 4,365,000 discloses certain polymeric aminopolysaccharide compositions used in the fabrication of contact lenses which are limited to graft and block copolymers of an acetyl glycosamine in combination with compounds selected from the group consisting of silicone collagen, acrylonitrile, acrylamide, alkyl methacrylates, alkylamino alkylmethacrylates, hydroxyalkyl methacrylates, pyrrolidones and vinyl derivatives of pyrrolidone.
Allan, U.S. Pat. No. 4,532,267 teaches a method for the production of hard or soft contact lens based on the aminopolysaccharide chitin.
Cellulose esters, especially cellulose acetate butyrate, have been disclosed for contact lens applications. These are not hydrogel materials, have relatively low oxygen permeabilities, and are not dimensionally stable.
Cellulose acetate butyrate (CAB) contact lenses are disclosed in U.S. Pat. No. 3,900,250.
Harris, et. al., U.S. Pat. No. 4,116,549 discloses a (CAB) lens material with an anti-warping treatment.
Neefe, U.S. Pat. No. 4,231,905 discloses a contact lens formed by dissolving a cellulose ester or ether in methyl methacrylate follcwed by polymerization.
Wittmann, et. al., U.S. Pat. No. 4,395,496 improved the dimensional stability of CAB by crosslinking it with trialkoxysilane methacrylates and diacrylates.
Loshack, et. al., U.S. Pat. No. 4,111,535 discloses a cellulose acetate propionate lens plasticized with dihexyl acrylate.
Lenses made from polymer blends of cellulose esters and ethylene/vinyl acetate have been disclosed with improved wettability compared to CAB lenses.
Wingler, U.S. Pat. No. 4,532,277 blends cellulose acetate butyrate with ethylene/vinyl acetate (EVA) to make a lens with 2% water content.
While cellulosics and polysaccharides bearing hydroxyl groups have been crosslinked with epichlorohydrin, diepoxides, acetals, diisocyanates, divinyl sulfone, and other hydroxyl reactive groups, hydrogel contact lenses composed of crosslinked hydroxyethyl cellulose are not disclosed in the prior art.
Previously, hydroxyethyl cellulose has been crosslinked with hydroxyl reactive groups such as epoxides, formaldehyde, glyoxal, dimethylol urea and the like.
Zemek et. al. Synth Polymer Membr, Proc. Microsymp Macromol., 29th, 1986, 463-9 synthesized membranes of hydroxyethyl cellulose by crosslinking it with 2-chloromethyl oxirane.
Masuda, JP 61/244369 A2, 10-30-86, discloses polysaccharide gels crosslinked with diepoxides.
Pokludova and Smejkal, Kozarstvi, 35(11), 329-34 crosslink hydroxyethyl cellulose for use in leather finishing, with Depremol M (4,5-dihydroxy-N,N'-dimethylolethylene urea).
Block, U.S. Pat. No. 4,473,479, crosslinks hydroxyethyl cellulose with glyoxal.
Stresinka, et. al., C.S.201185B disclose the use of 1-4 divalent hydroxamine acids as masked isocyanates for the crosslinking of hydroxyethyl cellulose.
Block, U.S. Pat. No. 4,366,070, reacts hydroxyethyl cellulose with formaldehyde to give a crosslinked system with good fluid loss and pseudoplasticity.
Shitama et. al., JP 54/22949 describe the manufacture of microcapsules by crosslinking hydroxyethyl cellulose with hexamethylene diisocyanate.
Pastyr and Kuniak, CS 172,160, describe a method for crosslinking hydroxyethyl cellulose fibers using dimethylolurea and glyoxal at 80.degree.-130.degree. C.
Pikler et. al., CS 166,076, crosslink hydroxyethyl cellulose with alkyl or aryl phosphites in dimethyl sulfoxide.
Pikler and Piklerova, CS 166,529, crosslink hydroxyethyl cellulose with Ce (IV) salts in the preparation of fibers and films with decreased water absorption.
The chemical reaction between hydroxyethyl cellulose and 2-isocyanatoethyl methacrylate in dimethyl sulfoxide had not been disclosed in the prior art. Ethylenically unsaturated cellulose esters have been disclosed by Grant, U.S. Pat. No. 4,565,857, for coating applications. In this case, the reaction of cellulose acetate butyrate containing 4.3% hydroxyl groups with 2-isocyanatoethyl methacrylate is used to make protective coatings for wood and other substrates.
Rama, et. al., U.S. Pat. No. 3,782,950, describe the reaction of hydroxypropyl cellulose with 2-isocyanatoethyl methacrylate for a reactive-type coating.
Goldenberg, U.S. Pat. No. 4,665,123 describes hydrogel contact lenses made from polyvinyl alcohol derivatives reacted with 2-isocyanatoethyl methacrylate in dimethyl sulfoxide solution and actinically crosslinked with (meth)acrylic monomers.
It is a further object of this invention to provide a means of crosslinking hydroxyethyl cellulose that provides crosslinked products of high mechanical strength at high water contents.
It is the object of this invention to provide cellulosic derivatives containing pendant (meth)acryloyl groups which are further reacted with a conventional vinylic monomer, and crosslinked to form a soft water-swellable hydrogel contact lens having high mechanical strength, high water content, superior optical clarity and high oxygen permeability.
It is a further object of the present invention to provide aqueous swollen contact lenses obviating, or substantially reducing, the drawbacks of the prior art.
It is a further object of the present invention to provide a method for preparing such contact lenses by crosslinking such cellulosic polymer containing (meth)acryloyl unit-vinylic monomer reaction products in an organic aprotic solvent in a mold, such as a spin cast mold or a static cast mold, and equilibrating the resulting aprotic solvent swollen contact lens in an aqueous medium.